In WDM (wavelength division multiplex) optical communication, multiple wavelengths of light each carry a communication signal. Each of the multiple wavelengths of light forms a WDM channel. In DWDM (dense WDM) optical communication, a subset of the WDM optical communication, the WDM channels are spaced closer together. A typical DWDM application operates at a wavelength band about 1,550 mm, has 90 channels, and has spacing of 0.4 nm between adjacent channels.
In the WDM optical communication there is a need to selectively block at least one of the WDM channels. In order to block a WDM channel, a dynamic range between a blocked WDM channel and non-blocked WDM channels must be at least 30 dB. Preferably, the dynamic range between the blocked WDM channel and the non-blocked WDM channels must be at least 40 dB. There is also a need to selectively equalize a power level of each of the non-blocked WDM channels.
What is needed is a method of selectively blocking WDM channels, which is fast, which is cost efficient, and which reduces a power level of a blocked WDM channel by at least 30 dB.